اَللَّهُمَّ أَنْجِزْ لِي مَا وَعَدْتَنِي اَللَّهُمَّ آتِ مَا وَعَدْتَنِي اَللَّهُمَّ إِنْ تُهْلِكْ هَذِهِ الْعِصَابَةَ مِنْ أَهْلِ الْإِسْلَامِ لَا تُعْبَدُ فِي الْأَرْضِ

Allaahumma anjiz li ma wa ‘adtani, Allaahumma aati ma wa ‘adtani, Allaahumma in tuhlik hadhi-hil 'ishabata min ahlil Islaami, la tu'badu fil ardi

O Allah! Fulfill what You promised for me. [O Allah! Bring about what You promised for me] O Allah! If you destroy this band of adherents to Islam, you will not be worshiped upon the earth. It has been narrated on the authority of `Umar bin al-Khattab (RA) who said: When it was the day on which the Battle of Badr was fought, the Messenger of Allah (ﷺ) cast a glance at the infidels, and they were one thousand while his own Companions were three hundred and nineteen. The Prophet (ﷺ) turned (his face) towards the Qibla. Then he stretched his hands and began his supplication to his Lord: (The dua mentioned above)

Reference: Muslim: 1763